The third episode of My Royal Nemesis begins with a flashback to the Joseon era, where Kang Dan-sim is plotting her revenge against the bullies. As the scene unfolds, two assassins suddenly attack Past Se-gye. When overpowered, one of the assassins kills himself while the other escapes. Past Se-gye assumes Kang is a spy until they recognize each other. She begs for mercy and asks for his name to thank him, but he rushes off to pursue the other assassin, leaving her hoping he'll be careful.
In the present, Kang fears that Mun-do might be the King and hides her face by hugging Se-gye. Se-gye is completely confused, while an amused Mun-do leaves them alone. The TV station staff are looking to scold her for running out and she pretends to faint. To avoid any more scandals, Se-gye plays along and carries her out. Since they are near his car, she gets in and demands that he drive her home. She then orders him to drive slowly since she's feeling carsick. Se-gye is annoyed but can't help but worry about her.
At the gas station, he hesitates before buying her medicine. He returns to find her gone with his credit card. From a public LED screen, Kang learns of the Chail Group and decides to keep her distance from Se-gye to protect herself from Mun-do.
Se-gye has bigger problems as he learns that his start-up, Biojei's main investor, Kaiserman Capital, actually belongs to Mun-do. One of Biojei's directors is a mole working with Mun-do, and they wonder who Shin Seo-ri is to Se-gye.
The story unfolds with tension and intrigue, as Kang and Se-gye navigate their complex relationships and the dangerous political landscape of the story's world.
Se-gye storms up to Mun-do, who reveals that he had earlier approached him to give him a heads up. Mun-do is actually quite slimy and always does his best to toy with and ruin Se-gye. This has been the case since they were kids. This time, Se-gye decides to hit back and use Kaiserman's money for Dynaestie's launch.
Back at home, Gwang-nam tries to keep Kang's share of the wages, causing a scene, but she simply grabs it from him. To thank him for his help, she offers him dinner, but he has a hot date. Only for his girlfriend to break up with him for another man.
At the street market, Kang learns the miracles of having a credit card and uses Se-gye's to buy her sweets. It turns out that Son has yet to cancel it. Se-gye is annoyed once again, but not enough to report her to the cops. Instead, he heads over to her place personally to retrieve his card.
From "desperately" asking her to sign Dynaestie's contract to showing up at her place, Kang thinks Se-gye is worried about her. This obviously flusters him, but yet again, he ends up tagging along when she ends up at a beef restaurant for a hearty meal. He pays for it and grills, all while grumbling.
They argue over English words like "romance," and he thinks Kang is just a method actress pretending to be a Joseon woman. Before they part ways, he frets over her welfare. She is touched and realizes that he is actually a decent human being.
As for him, the radio keeps playing love songs while he sees Kang everywhere, flustering him further.
Elsewhere, Mun-do and his uncle, Dal-su, are fishing. Dal-su praises Mun-do for how he is running Chail and wishes Se-gye was like him. Mun-do hints that Se-gye is distracted because he is dating a woman.
Returning home, Kang discovers a heartbroken Gwang-nam and scoffs at her lack of understanding of love. As she researches "romance," she's upset that both Se-gye and Gwang-nam treat her like a fool, leading her to ponder the past version of Se-gye. In a flashback, she serves as his court lady, unafraid of the rumors surrounding him due to his single eye. He asks for her name, and Se-gye dreams of the same memory, waking up with a tear. He recognizes Kang as Shin Seo-ri and confides in his psychiatrist friend, Jeong-hyeon, who claims he must be in love. This irritates Se-gye, who sees Kang as a thorn in his side.
Meanwhile, Dal-su asks Son about Se-gye's girlfriend, and Son insists that Se-gye has no one, confidently stating that he would never date Seo-ri. Kang and Gwang-nam are busy with another part-time gig at a mall. In the electronics section, she sees Ji-hyo overacting as a queen in a historical drama. Kang reenacts the scene as true royalty would, delighting passersby. Another TV plays young Seo-ri's show, and her heartwrenching performance moves Kang. Surprised that TV shows have the power to make someone feel things, she decides to repay Seo-ri by pursuing her dream of acting.
However, the board must choose Dynaestie's spokesperson. One half wants Ji-hyo, while Mun-do's mole insists on Seo-ri. They debate heatedly, with Se-gye secretly rooting for Seo-ri. He practically jumps for joy when the final vote is in her favor. However, Seo-ri's agency, Doran Entertainment, hasn't actually terminated her contract. CEO Hong refuses to allow her the Dynaestie gig, pushing for Ji-hyo instead. Se-gye worries for Kang and feels embarrassed when he realizes she's used to rejection. Just then, Kang calls, accepting the gig after being won over by his sincerity. He feels bad as he tries to tell her the bad news but fails.
She shows up at Biojei and even thanks the receptionist for leading her to the audition. There she runs into CEO Hong and Ji-hyo. A physical fight is instigated by Ji-hyo while Se-gye impatiently waits for Kang. He finally shows up and is upset by the marks on Kang's face. He speaks just like the past version of Se-gye as he reveals that he will represent Kang with his newly launched entertainment agency. He grabs her hand and shakes it, sealing the deal. As he smiles, Kang gets butterflies.
In a flashback, it's revealed that the King assigned Kang to his brother, Prince Cheongheon (the past version of Se-gye). The King would use her to trap Cheongheon. Coincidentally, Mun-do has the same plan to cause havoc by using Seo-ri against Se-gye. In another flashback, when Se-gye learns of Ji-hyo slapping Kang, he fixes his hair and runs to save Kang.
